Toward a Sub-Decibel Noise Figure Broadband Monolithic LNA in Silicon

This paper reports a first attempt toward realization of a single-chip silicon-based broadband (BW_-3dB > 5 GHz) low-noise amplifier (LNA) with a noise figure (NF) of less than 1 dB across the band. A differential common-emitter amplifier with active feedback and neutralization capacitance is adopted without using passives at the input that consume chip area and deteriorate NF due to their loss. Design tradeoffs for NF, gain, and bandwidth versus device size, bias current, and process corners are discussed in detail. The circuit was implemented in a 0.13-mum SiGe BiCMOS process with f_T = 200 GHz and f_max = 244 GHz for an HBT with emitter length of 6 mum and bias current of 7.6 mA. The differential probed measurement of the LNA shows a gain of 27.5 dB with -3-dB bandwidth from 0.5 to 5.5 GHz. The NF varies from 1.35 to 1.85 dB within the band. The chip is also packaged in a high-frequency package with subminiature A connectors for inputs and outputs. The single-ended packaged measurement of the LNA shows a gain of 25.2 dB with -3-dB bandwidth from 0.5 to 6.0 GHz. The NF varies from 1.2 to 1.7 dB within the band. The chip draws 24 mA from a 2-V supply and occupies 0.88 mm times 0.83 mm.